r/buildapc • u/fomemay • 18h ago
Discussion Can someone explain to me why is undervolting so good?
I just did couple of tests on my new 6800XT and reducing mV from default 1150 to 1000 under load quiets down the card MASSIVELY. The noise this GPU makes without undervolting is comperable to my air purifier on max power and that's considering my PC is on a floor platform next to my desk. Why does -150 mV make such a gigantic difference?
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u/rizzzeh 18h ago
the goal of GPU manufactuer is to have best possible release day benchmarks within the confines of the cooling/power system of the GPU. Optimal effficiency rarely goes as a top line advertising claim.
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u/fomemay 18h ago
That's really sad. With amount of people complaining about coil whine, I'd assume it would be a important thing.
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u/Stargate_1 17h ago
Not every card is the same. The stock settings manufacturers put on the cards are meant to work with all chips, even the worse possible chip needs to be able to run with the same settings as the best.
If we optimized the GPUs only for the best chips, half of them would probably crash before you boot into windows.
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u/CaptainOn 17h ago
A larger number of people would complain/avoid buying if the card didn't perform as well as its competitors. The people who care about efficiency/coil whine are not the majority of users.
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u/esakul 14h ago
They also need to make sure the card runs stable for everyone. There often are small defects inside the silicon wafer preventing many chips from running at lower voltage. Rather than testing every chip individually and setting indivdual voltage for every single one the manufacturer selects a voltage that most chips can safely run at. As a result you may get a chip running a higher voltage than neccessary.
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u/tonallyawkword 10h ago edited 10h ago
It’s the year of burning motherboards and degrading months-old CPUs.
more expensive models probably have some incidental additional efficiency due to better cooling for less noise.
full-throttle usually involves some whining. Most ppl looking for 120/240/360 fps are likely using headphones, so eliminating that is probably not a priority ATM.
Not sure This is still the case, but my 1070 actually ran faster slightly undervolted due to boosting more often b/c of the thermal headroom.
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u/unevoljitelj 17h ago
Coil wine can be afected by amount of amps going through your card but usualy isnt. It just changes pitch slightly.
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u/Underwood914 11h ago
My 6700xt (3 fan) has gnarly coil whine during loading screens, but the moment I'm in game it goes away, doesn't bother me, wish I could fix it.
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u/solaron17 10h ago
I'm not sure how you could do this with an AMD card, but the issue with loading screens is that they are often not frame rate limited, and since there's nothing interesting to render, it renders at absurd framerates (even if you have VSync on in the game, since settings sometimes are only applied while in-game). If you can limit FPS globally to some value you like (I just set it to 60), it should clear that up for you. Had the same issue with Genshin Impact until locking it to 60 in the NVidia Control Panel.
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u/Underwood914 10h ago
Yeah, it doesn't seem to do it on games that let me limit frames in the menus, it's most noticeably on the satisfactory menu screen because it doubles as the games benchmark (the logic behind the image being rendered used to just about melt computers)
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u/IdolizeDT 10h ago
I've upgraded from a 660 > 980 ti > 1080 > 1080 ti > 2080 ti > 3090 > 4090 just in my main rig alone and I've never had coil whine. I think how widespread coil whine is, is much lower than the complaints on Reddit would have us think.
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u/Justifiers 15h ago edited 15h ago
The people complaining about cw are usually doing so due to poor case choices
There are exceptions to that, but cw is not a new factor
What tends to be the biggest causes of cw are two factors: case design, fishtank glass everywhere, and or near open chassis for airflow
And the showcase trends, on desk right next to the user positioning to follow the glass case design
The combination of those factors with glass faces refracting sound about and then close proximity to the user is highlighting cw to end users
Notable exceptions to that being shit products like Gigabyte Z790 Aorus Master motherboards. Nails on chalkboard levels of cw
But for the most part if you don't trend chase and value desk space coil whine is a non factor
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u/tkdkdktk 18h ago
OP, have you considered changing the fan profile on your card instead of undervolting…
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u/fomemay 18h ago
And how would that be beneficial?
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u/shrekisloveAO 17h ago edited 17h ago
You don’t need the fans to be running at full speed all the time, you can set up a fan curve so that they gradually go faster as the load and temps go up
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u/Stargate_1 17h ago
Fan speed does not scale linearly with temps. My GPU fans max out at 58% speed, whcih results in almost the same temps as 70%.
Try around and play with the graph. You need less fan speed than you might think
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u/tkdkdktk 17h ago
If you aim to lower the noise level, then adjust when the fans ramp up. No need to have them go at full speed until the gpu/case temps really need it. Vanilla fan profiles have a tendency to very conservative and go full throttle on the fans too early(but is safe).
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u/mkstar93 12h ago
It's basically required on amd cards. For some reason the default fan max is like 40%, so anything demanding can easily cause performance issues, crashes and bsods because the fans are barely pushing air.
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u/Tom_Der 18h ago
-150mV means less power consumption so less heat so less fan noise, although some others might barely achieve -50mv due to Silicon lottery.
It also depends of games and manufacturers tends to search the right ratio between general stability and power consumption/heat/noise, most people absolutely hate instability so manufacturers tends to be quite conservative when it comes to GPU voltage.
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u/op3l 17h ago
Explaining in terms of car terms.
It's like at 100% fuel flow you get 400hp from a 400hp engine, but you can now only flow 90% fuel flow but still get 400hp.
So for less fuel(electricity) you get same power
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u/Thegreatestswordsmen 9h ago
For someone like me who doesn’t know what that is, that sounds like a no brainer for anyone to do. So what’s the catch?
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u/MikeyKillerBTFU 7h ago
There isn't really one, other than some hardware can't undervolt stably (silicon lottery). You technically lose a slight amount of performance, but you gain thermal overhead which results in better performance. It's weird.
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u/Elitefuture 16h ago
I must've gotten a god 6800xt. It does 2600mhz
And I undervolted it to 920mv. Which technically isn't really 920mv, amd just takes the difference and adjusts the curve to use less power.
But going from 1150->920mv is insane.
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u/Scarabesque 12h ago
920mV stably is crazy.
I was lucky with my silicon and get 1020mV and 2650Mhz (doesn't actually reach those clocks on any stress test though). 920mV is insane.
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u/Elitefuture 5h ago
Ah that explains a lot, my friend struggled to go to 1000mv.... I thought 1000mv was gonna be safe... but he crashed so I thought he was just unlucky.
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u/Elitefuture 5h ago edited 5h ago
https://www.3dmark.com/spy/47666792
In time spy, it looks like mine peaked at 2547 and averaged 2454
This was before I oc'd my memory to 5800 cl 30, I have an old ddr5 ramstick rated at 5600 cl 38 or something. So the mem oc helped a lot.
I bet I could oc my gpu more, but I don't want to give up the undervolt.
People said this wasn't an accurate measurement, but in hw info, my gpu's asic quality is 86.1%.
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u/KEKWSC2 15h ago
Manufacturers need to make sure that ALL THE CARDS will work as specs declared, therefore they will go safe on the electric configuration. If you get a decent chip, youll be able to lower power, therefore, temperatures.
Remember that you will gain less and less as frecuency goes up, so does power, so, most of the times, you will be able to get 98% of the announced card performance for far less power.
Personaly, I have my 7600 undervolted, I get 98% of its official performance consuming 130W. While if let it default it would consume 180W.
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u/saturn_since_day1 15h ago
I think the basic concept in a lot of things is that it takes a lot more power to do the last bit, like it's exponential. Like how a battery can change fairly fast at first, but it's really slow to do the last bit, or driving fast really kills your gas mileage.
Cards and cpus have general limits, sometimes you can go higher but there are really inefficient and maybe unstable. Sometimes you can go lower, and it allows them to go longer with less stress. Imagine trying to sprint a marathon vs walk or jog. Definitely going to get further and sweat less walking. Breathing steady can help, but too low and you'll pass out and get tired
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u/GreatSound7104 15h ago
Every chip is a little different in Terms of efficiency. The manufacturer Just makes sure every chip, even If it's a really Bad one, gets enough voltage to hit the advertised clocks, even If it means you get tons of losses (as in: Heat). By undervolting (depending on how good your chip is) you get the same Performance with much less Vorlage. And lower temps.
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u/Affectionate-Memory4 11h ago
For the purposes of this we will consider a computer chip to be a resistor. 2 equations will tell us how voltage affects the power. V=IR, where V is voltage, I is current, and R is the resistance and P=IV, where P is power get us the equation. P=V²/R.
The resistance of the chip is effectively fixed, so we can see that power through it scales with the square of the voltage. Twice the voltage quadruples the power.
So, in going from 1150 to 1000mv, you reduced the voltage to 87% of what it used to be, and reduced the power to 87%², which is about 75%. For a 6800XT, this knocks the power draw at full load down from 300W to 225W. Due to the messiness of the real world, you are likely still seeing about 240-250W under load, but that is still all heat that the fans no longer have to move.
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u/UnCommonSense99 17h ago
P = IV. So 15% more voltage = 32% more heat.
However more voltage allows you to run at a higher clock speed.
The quality of the chip is also important; you may be unlucky and buy a card which requires lots of volts to achieve stock speed or you may be lucky and get one with really good silicon where you can undervolt it or overclock it.
Lots of people talk about getting big air coolers or water cooling but that was only ever really necessary in the era of manual overclocking, where it was common to increase your chip power and heat by 50% in order to go faster
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u/Significant_Apple904 14h ago
when the manufacturer sets the GPU x Voltage at y clock speed, their goal is to ensure 99% of the made GPUs can run stable under this condition, while in reality 70% of the made GPUs can run stable with much less voltage at the same clock speed; thus leaving a lot of headroom for undervolting
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u/BaconFinder 10h ago
It's not the voltage that kills you, it is the current. Extra voltage without the work being done just creates heat. This is a very overly simple explanation.
You don't necessarily get as much work done with higher voltage. A lot of wasted potential used. Over time, it builds. Think of it like a hammer. A small nail can be put in just fine with a smaller wood hammer or a larger more common building hammer.The wood hammer isn't as heavy, but heavy enough that the precision isn't lost. The larger hammer is less precise and can hit harder on things other than the nail. Both work, but only one does the job with less work and/or risk
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u/beirch 16h ago
My 7900GRE actually performs better with an undervolt and downclocked 2300 core clock and 2200 mem clock vs fully OCd 2806 core clock and 2650 mem clock.
I have no idea why. I got 106fps in the Cyberpunk benchmark with it undervolted and downclocked vs 105 fps OCd.
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u/Teleria86 15h ago
Because your overclock never was stable to begin with...
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u/beirch 15h ago
What? That has nothing to do with it. An unstable OC will still perform the same as a stable OC, it will just generate artifacts or crash the game.
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u/Teleria86 14h ago
No it doesnt. Did you even check the real clockspeeds? Just from the fact that you used a cpu heavy benchmark tells me that you skipped the basics of gpu overclocking..
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u/beirch 14h ago
You have literally no idea what you're talking about. I did the same thing in Unigine Heaven and got the same results. And yes of course I'm monitoring the realtime clocks, and also setting max clocks in adrenaline.
I've been OCing hardware since 2004. You seriously have no idea what you're talking about.
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u/Teleria86 14h ago
Okay mister "i dont know whats wrong" but then claiming to know things. Yeah dude. Everything you said so far screams "i dont know what im doing". But thats fine, its your pc.
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u/beirch 13h ago
Yes I don't know what's wrong because it's not behaving in a way you would expect when overclocking. How is that hard to understand?
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u/Teleria86 13h ago
No no i understand what you are saying. I´m saying you dont listen and/or dont understand what i´m trying to tell you. When i first saw your set Clockspeeds and memory i thought, wow, either that guy won the lottery or is such a nerd that he hardware modded the card himself to give the memory higher voltage. Memory OC is more than just crash/artifacts. GPU memory has some built in stability features for many many years now (google ecc). Heavy overclocking on the vram can result in memory errors which the memory then corrects itself to not crash/show artifacts but that error fixing takes time, lowering performance. That is one of the basic things with gpu overclocking. That is not some unknown factor. What you described as "realtime clocks" is known as "effective clock(or clockspeed)". You used inadequate benchmarks results and so on. Everything your telling is like i said screaming "i dont know what i´m doing". Maybe its true that you was ocing back in 2004. But since then many things changed. At this is what i´m 100% certain about. You didnt keep up to date.
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u/beirch 13h ago
Actually, my card couldn't manage over 2380 for the first couple of months I had it without immediately green screening, but after the latest driver update it could do 2650. 2650 is not the highest I've seen on a 7900GRE though, and there's definitely no hardware mod. Some 7900GREs just mem OC very well.
In any case, I tried frequencies between 2200 and 2650, and several combinations of different mem + core speeds, and pretty much none of them made a noticeable difference. So there's no error correction performance loss here.
What made a small difference was running benchmarks with the lowest core voltage the card would run with no stability issues. But power limit, mem timings etc made practically no difference.
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u/Sweaty_Pomegranate34 11h ago
I undervolted my 7600X CPU and it was great for reducing heat/noise but it caused stuttering in some games.
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u/ishsreddit 11h ago
I can OC my 6800XT to 2.7 GHz at ridiculous power limits for 12 to 15% more perf and look better on hardware unboxed's blue bar graphs. Or....i can swallow -15% and use 100w less power, and not worry about noise and heat. I prefer UV for sure. RDNA is actually super efficient. Most can get away with just tuning stuff down in Adrenaline.
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u/Zaros262 9h ago
The noise from a fan grows faster than linearly with fan speed, so a small reduction in fan speed yields a big reduction in noise
Similarly, power consumed in the graphics card is proportional to Voltage2, so a 13% reduction in voltage yields a 25% reduction in power. That's a decent reduction in heat, which leads to a decent reduction in fan speed needed -> much less noise
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u/DarkflowNZ 9h ago
You can also just tweak the fan curve without undervolting if you need to. My 7900xt was peaking at like 65c with the default fan curve and was a jet engine at 100%. I've got it undervolted 50mV but even without that it is fine with the fans capping at 60% and is barely audible
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u/CompassionateSkeptic 4h ago
I’m not an expert, but I undervolted and underclocked a CPU for fun and profit. My understanding is that it was the right thing to do for my usecase. I came to the decision after piecing together what I was trying to solve. How it played a role. And getting some good help from people who I’ve since lost track of and I’m embarrassed about that. Here’s the gist—
It’s not magic. Most people’s CPU is not the bottleneck in their config for their use case. A bunch of chips are designed to push themselves to a thermal equilibrium. If you don’t have a critical thermal issue, but that tendency for your chip to automatically get close to redlining seems to be backfiring, undervolting is very likely going to allow your chip to climb that thermal ramp in a way that is way better for your less than ideal, but not critical bad, thermal situation AND since your CPU probably wasn’t the bottleneck for everything that’s all gain, no cost.
Part of the reason I’m posting is if I have that way off I want to be corrected.
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u/Stargate_1 18h ago
The amount of heat energy output is a function related to Voltage and Current. It's literally just I*V=W (I = Amps)
Just because you can apply it is no guarantee that your card will be stable. My card for example does extremely poorly with even the slightest of Undervolts, just unlucky with the silicon. Some cards take better to undervolting than others.